High pressure metal to metal seals have been used as shown in U.S. Pat. No. 6,098,717. These seals are actuated by internal expansion and can be fitted with one or more seals. Another example is U.S. Pat. No. 5,333,692. In this patent the seal ring is expanded with a tapered swage and the outer surface of the ring has extending members initially covered with a seal. Radial expansion brings the fingers through the seal material for metal to metal contact with the surrounding tubular as the seal element is contained between the extending members. These designs have been reliable and have been in regular use for at least 10 years or more.
More recently the service pressure differentials have gotten larger as the wells have been drilled to greater depths. As a result the seal bodies exhibited limitations on seal containment due to the stresses they could tolerate with the needed amount of radial expansion and pressure differentials. Efforts were focused at seal configurations that would improve seal containment by reducing stress on the seal body at the anticipated differential pressures and the amount of radial expansion.
The present invention has focused on features of the seal body that improves seal containment with reducing the stresses by providing an exterior bump between exterior seal elements that is opposed to an interior seal and internal bumps opposed to spaced external seals. The bumps feature end transitional surfaces that provide an extrusion volume for the seal which allows effective seal containment at the anticipated differential pressures and the amount of radial expansion. The seal configuration can be reversed with one exterior seal and two axially offset interior seals. Another feature of the invention is stacks of seal rings can be deployed between end rings preferably made of high performance thermoplastics or metal so that not only can each seal ring back up other rings but the stack of seal rings can expand independently to deal with dimensional irregularities in the surrounding tubular or the mandrel being expanded, hence creates effective sealing. These and other aspects of the present invention will be more apparent to those skilled in the art from a review of the description of the preferred embodiment and associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims.